Here's your Latin lesson for the day: somnus in Latin means “sleep.” If you tack the prefix “in-” (another Latin word, meaning “not”) onto it, you get a word that means “not sleep.” An insomniac, therefore, is a person who suffers from the inability to sleep. Once you know the Latin root somn-, which you now do, then you will also recognize it in some related words—somnolent, meaning “sleepy, drowsy,” somniferous, meaning “sleep-inducing,” and somnambulate, meaning “to sleepwalk.” By now, you can probably guess that a somnambulist is a sleepwalker. Perhaps the most famous somnambulist is Cesare, a carnival attraction in the 1920 silent film The Cabinet of Doctor Caligari. We hope this story hasn’t been too somniferous—but, if it has, pleasant dreams!

Popular references

—Insomniac: An album by the punk band Green Day, released in 1995.

—Insomniac with Dave Attell: A Comedy Central television show, hosted by Dave Attell, which ran in the early 2000s.

Related Quotations

“The more the insomniac tries to go to sleep, the wider awake he becomes.“ —Andre Muller Weitzenhoffer, The Practice of Hypnotism(2000)

“In the morning she put on her black dress again, and carried her insomniac face proudly to the breakfast table, where Melissy took one look at it and rang up the doctor immediately.“ —Elizabeth Stuart Phelps, “Twenty-Four Four“ Harper’s New Monthly Magazine, Volume 92, Issue 1(December 1895 to May 1896)